Remove the unused realtime WebRTC crate (#33639)

## What changed

- Remove `codex-realtime-webrtc` from the Cargo workspace and Bazel build,
  along with its native WebRTC dependency graph.
- Use `blake3`'s pure Rust implementation on
  `x86_64-pc-windows-gnullvm`, where the Bazel lint toolchain cannot
  reliably materialize the crate's native x86 assembly archives.

GitOrigin-RevId: c382d888cd7ada7a17a7a0dcbdecbe00744f5055

MODULE.bazel

@@ -220,6 +220,13 @@ crate.from_cargo(
 
 bazel_dep(name = "zstd", version = "1.5.7")
 
+crate.annotation(
+    # The Windows lint toolchain cannot reliably materialize blake3's native x86 assembly archives.
+    crate = "blake3",
+    crate_features_select = {
+        "x86_64-pc-windows-gnullvm": ["pure"],
+    },
+)
 crate.annotation(
     crate = "zstd-sys",
     gen_build_script = "on",